Speed-controlling device



E. H. GREIBACH SPEED CONTROLLING DEVICE June 12, 1934'.

Filed Nov; 6, 1928 2 Sheets-Sheet *1 INVENTOR Z2217 x? rzzfiazi ATTORNEY June Z, 1934.

E. H. GREIBACH SPEED CONTROLLING DEVICE Filed Nov. 6, 1.928 2 Sheets-Sheet 2 lNVENTR E7722] 164 671525 ac/a.

ATTo RN Patented June 12, 1934 PATENT OFFICE- SPEED-CONTROLLING DEVICE Emil H. Grelbach, Pittsburgh, Pa.,' assignor to Westinghouse Electric 8; Manufacturing Company, a corporation of Pennsylvania Application November 6, 1928, Serial No. 317,682

My invention relates to speed-controlling devices, and it has particular relation to such devices when embodied in' apparatus for sound recording andr'eproducing.

During the photographic recording of sound on a film by means of light that fluctuates in accordance therewith, and during the reproduction'of, the sound from the record throughthe use of a photo-sensitive cell, it is highly essential that the film shall be caused to travel past the recording point, or the reproducing point, at a speed that does not varyat an audible rate.

It has previously been suggested that constant film-speed could be secured by associating a relatively heavy fly-wheel with the sprocket wheel that pulls the film throughthe apparatus, and it has also been suggested that beneficial results might be obtained by passing the film over an idler connected to a fiy-wheel. By reason of the fact, however, that the film, if of the combined sound-and-picture type, or if it is to later be utilized for transferring the sound to an ordinary motion-picture film, must not be pulled through the apparatus at a speed greater than about one and one half feet per second, a circumferential velocity cannot be given to the fly-wheel that is sufficiently high to compensate for speed variations of the driving means.- I v By interposing a spring between the driving motor and the fly-wheel connected to the filmpullin'g sprocket, as shown in GermanPatent 389,311 the drawback of low. fly-wheel velocity is, to some extent, at least, overcome. Unfortunately, however, the spring and fly-wheel constitutean oscillatory system which, if energized by impulses near, or at, its natural period, tends to introduce variations into the rate of filmtravel which manifest themselves in unpleasant changes in pitch when the recorded sounds are reproduced.

It is, accordingly, an object of my invention to provide means whereby a sound-record blank shall be caused to travel through a sound-recording device at constant speed.

Another object of my invention is to provide means whereby a sound-record shall be caused 'to travel through a sound-reproducing device at a constant speed.

Another object of my invention is to provide a mechanical filter suitable for incorporation into any device wherein unvarying peripheral speed of a rotating element is essential.

Another, and more specific, object of my invention is to provide, in a mechanical filter 8 Claims. (Cl. Wil -2.3)

having a natural period of oscillation, viscous means for damping such oscillations.

In carrying my invention into effect, I affix a fly-wheel to the shaft on which is mounted a film-pulling sprocket, or an analogous element, and convey rotary motion to the fly-wheel, from a prime mover, through a spring device. In order that the fly-wheel shall not oscillate at the natural period of the system constituted by it and the spring, and to prevent minor variations in the load; or of the actuating force, from causing the peripheral velocity of the flywheel to vary, I supply a damping load thereto in excess of the load imposed by the friction of the sound-record blank, or of the sound record, through the apparatus.

"The novel features that I consider characteristic of my invention are set forth with particu-- larity in the appended claims. Theinvention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of a specific embodiment, when read in connection with the accompanying drawings, in which: 80

Figure 1 is a view, partly in perspective, of the essential elements of a preferred embodiment of my invention,

Fig. 2 is a view, partly in elevation and partly in cross-section, of the elements shown in Fig. 1,

Fig. 3 is a view, in elevation, of one of the details of the device.

Fig. 4 is a view in perspective showing a' modification of my invention, and

Fig. 5 is a view in elevation showing an element of the system shown in Fig. 4 with its dimensions considerably reduced.-

The apparatus illustrated in the drawings comprises a film-pulling sprocket 1 which is aflixed to one end of a shaft 2 that turns in suitable bearings 3 and 4. A fly-wheel 5 is mounted on the shaft intermediate the bearings and is held thereon by a plurality of screws 6 extending through a shoulder 7 machined on the shaft.

A gear 8, having a shoulder 10,- is loosely mounted on the shaft 2 intermediate the bear-' ing 4 nearest the sprocket and the fly-wheel. The shoulder is provided with a flattened pertion 11 to which is affixed one end of a spiral spring 12 that is disposed in a recess 13 in the face of the fly-wheel nearest the gear 8. The other end of the spring is afllxed to the flywheel by means of a pin 14 which extends through a loop formed in the said end.

Rotary motion is transmitted to the gear 8 (not shown) is connected through a mechanical from a prime mover (not shown), which may be either an electric motor, a hand operated crank,

or the like, and from the gear to the fiy-wheel through the spiral spring. The strain imposed on the device when starting or stopping is taken up by a plate afiixed to the gear by a plurality of screws 16, the peripheral portions 17 of the plate being so disposed as to come into contact with a plurality .of pins 18 carried by the fly-wheel when the spring is too tightly wound up or when the fly-wheel tends to overrun the gear, as shown in Fig. 3.

The apparatus thus far described operates in a fairly satisfactory manner to cause uniform rotary motion of the sprocket when power is applied to the gear from a steady source but it is inadequate for the purpose of drawing an unexposed film past the sound-recording point, or of drawing a film past the reproducing point in a film-phonograph, or the like.

In sound-recording-and-reproducing apparatus approximate uniformity of film-travel, such as is obtained by the combination of spring and fiy-wheel, is notenough, since the slightest variation in the speed of the film through the apparatus will result in a distorted record, on the one hand, and distorted reproduction, on the other.

I have, therefore, added a viscous braking, or damping, device to the apparatus, the said device comprising a leather ring 20 that is held against one face of the fiy-wheel by a plate 21. The plate and the surface of the fiy-wheel against which the leather ring bears are severally provided with an annular channel 22, the channel in. the plate being kept filled with oil through a tube 23 which connects therewith, and the channel in the fiy-wheel being supplied with oil by seepage through the leather ring.

The plate 21 is provided with upper and lower guide-ways 24 which cooperate with upper and lower rails 25 to maintain the plate always parallel with the face of the fly-wheel. Portions of the upper rail are omitted from the drawings for the sake of clarity.

Pressure is applied to the plateby a. pivoted fixedly-supported pin 27. A spiral spring 28 surrounds the pin, one end of the spring bearing on the free end of the member .26 to exert pres-- sure thereon, and the other end of the spring bearing on an adjustable nut 30 which may be moved to alter the pressure.

The complete device, as illustrated, is analogous to an electrical filter system, the flywheel being equivalent to an inductor connected in series with a resistive load imposed by the film on the sprocket and the resistive load imposed by the various bearings, etc. The spring is equivalent to a capacitor connected in shunt to the load, and the viscous dampin device is the counterpart of a resistance added in series with the load. It is believed obvious that a plurality of such filter systems could-be utilized in series if desirable, instead of the single one illustrated.

It is' highlyimportant that the natural frequency of the oscillatory system constituted by the inertia member, or fly-wheel, and the compliance member, or spring, shall be kept below the frequency of any vibrations that tend to arise in the entire apparatus.

In an alternative form of my invention, that is illustrated in Figs. 4 and 5, the prime mover filter of the type shown in Figs. 1, 2 and 3 to a film-driving sprocket wheel, as shown in the latter views, and another fiy-wheel 40, with an accompanying damping device 42, is connected to an idler-roll 44 through a resilient coupling 46, over which the film 47 passes at, or near, the sound-recording or sound-reproducing point. It is also advisable to provide a slight amount of slack between the film-advancing sprocket and the idler-roll 44, and this may be accomplished by causing the film 47 to pass over a resiliently supported idler-roll 48. In such event, the fiy-wheel'40 and the resilient member 46 are preferably so proportioned that their natural period is substantially the same as the frequency of the impulses imposed, through the film 47, on the idler-roll 44 by the reaction between the perforations 50 of the film 4'7 and the sprocket-teeth 52, i. e., 96 cycles per second, since they then function as a parallel-tuned circuit offering high impedance to the said frequency, and serve to maintain the idler-roll 44 rotating at a uniform velocity.

I have established, by research and experiment, that ordinary frictional damping is ineffective to maintain the fly-wheel at a constant speed, in apparatus of the type shown in the drawings. The braking force must always be proportional to the velocity of the fly-wheel, and not independent thereof, since such a force only can properly oppose variations in velocity caused by oscillations. A braking force of the required character is supplied by an oil-film, or by a film of any other material having the property of viscosity, and my invention is, therefore, not limited to the use of oil alone.

The advantages of my invention will be readily apparent to those skilled in the art. By associating a mechanical filter, of the type described, with the film-pulling sprocket of sound-recording apparatus, or with. an equivalent sprocket in sound-reproducing apparatus, I am enabled to very markedly improve the'quality of the sound record and the sound reproduction therefrom.

My invention is not restricted to use in con- 'nection with sprocket wheels, however,. but is equally as well applicable to smooth drums, when utilized in apparatus of the type hereinbefore referred to, and it is also applicable to apparatus of any type wherein it is desired to maintain a driven member in motion at a constant velocity, irrespective of vibrations set up through any cause whatsoever.

Inasmuch as many modifications of my invention will be suggested to those skilled in the art to which it pertains, it is not to be restricted to the specific example chosen for purposes of explanation but is to be limited only by the prior art and by the spirit of the appended claims.

I claim as my invention:

1. In combination, a rotatable member, a flywheel afflxed thereto to rotate therewith, means, including a resilient member, for imparting rotation to said flywheel, and viscous damping means including a lubricant-absorbing medium imposing a load on said fiy-wheel.--

2. In combination in web advancing apparatus, means for advancing a web, said means being of such character that as it cooperates with the web a periodic disturbance is intro-. duced in the movement of the web, means for motivating said advancing means, a mechanical filter interposed between said web-advancing means and said motivating-means for said web- 150 advancing means whereby said web-advancing means is maintained in uniform motion, means to be motivated by said web as it is advanced by said web-advancing means and a mechanical filter, having a natural frequency substantially equivalent to the principal frequency of the disturbance that arises by the cooperation of said web and said web advancing means, cooperating Withsaid means motivated by said web advancing means to maintain said web in uniform motion.

3. In combination in web advancing appara tus, a roller equipped with dentate means for advancing a web, means for rotating said roller, means to cooperate with said roller and said rotating means for maintaining the angular velocity of said roller uniform, another roller to be rotated by said web, and a mechanical filter, having a natural frequency substantially equivalent to the frequency of the disturbance introduced into said web by the cooperation of said dentate means and said web, cooperating with being so related to said mass that the natural frequency of said filter is substantially equivalent to the frequency of the disturbance introduced into said web by the cooperation of said dentate means and said web, said filter cooperating with said last-named roller to maintain said web in uniform motion.

5. In combination in web advancing apparatus, a roller equipped with dentate means for advancing a web, means for rotating said roller, means to cooperate with said roller and said rotating means for maintaining the angular velocity of said roller uniform, another roller to be rotated by said web, and a mechanical filter, comprising an inertial mass, means for resiliently coupling said mass to said last-named roller whereby said mass is rotated as said roller is rotated and means for damping the free movemerit of said mass, the elastic constant of said coupling being so related to said mass that the natural frequency of sai filter is substantially equivalent to the frequency of the disturbance introduced into said web by the cooperation of said dentate means and said web, said filter cooperating with said last-named roller to maintain said web in uniform motion.

6. in combination in web advancing apparatus, a roller for advancing a web, an. inertial mass to be rotated with said roller, means for rotating said inertial mass and saidroller, said means being of a character tending to introduce periodic variations in. the motion of said roller, resilient means for coupling said inertial mass to said rotating means whereby said inertial mass and said roller are rotated, the elastic constant of said coupling means being so related to said inertial mass that the natural frequency of the mechanical system comprising said mass and said coupling means is less than the smallest frequency of said periodic variations, and means for damping the free movement of said mass.

7. In combination in web advancing apparatus, a roller for advancing a web, an inertial mass to be rotated with said roller, means for rotating said inertial mass and said roller, said means being of a character tending to introduce periodic variations in the motion of said roller, resilient means for coupling said inertial mass to said rotating means whereby said inertial mass and said roller are rotated, the elastic constant of said coupling means being so related to said inertial mass that the natural frequency of the mechanical system comprising said mass and said coupling means is less than the smallest frequency of said periodic variations, and viscous. damping means including a lubricantabsorbing medium'for damping the free movement of said mass.

till

lltlll 8. In apparatus of the type comprising a responding frequency is substantially less than the frequency of said periodic forces and stationary means for damping said filter system.- EMIL H. GREIBACH. 

